455 grams / 1 Lb The chemical formula for washing soda is Na2CO3 or sodium carbonate. It is a salt of carbonic acid, a chemical which produces a wide range of salts collectively known as carbonates. One common source of washing soda is the ashes of burned plants; for this reason, it is sometimes called soda ash. The sodium carbonate "softens" water helping other cleaning ingredients lift soil from the fabrics and suspend the soil in the wash water.The washing soda binds to the minerals which make water hard and allows the detergent to be absorbed into fibers properly to clean clothes.